Chapter 2 Infective Conjunctivitis – Its Pathogenesis, Management and Complications Adnaan Haq, Haseebullah Wardak and Narbeh Kraskian Additional information is available at the end of the chapter http://dx.doi.org/10.5772/52462 1. Introduction The aims of this chapter are to briefly discuss infective conjunctivitis, its subtypes and its treatment. Other forms of conjunctivitis will also be considered and discussed in this chap‐ ter, namely, neonatal conjunctivitis, conjunctivitis in the immunocompromised. A compre‐ hensive assessment of the various treatments of conjunctivitis will also be discussed. Conjunctivitis is a term broadly used to describe an inflammation of the conjunctiva. Con‐ junctivitis may be split into four main aspects; bacterial, viral, allergic and irritant. Infective conjunctivitis, namely bacterial and viral will be discussed in this chapter in details. Figure 1. The conjunctiva in relation to the orbit and its structures © 2013 Haq et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 22 Common Eye Infections 1.1. Anatomy of the conjunctiva The conjunctiva is the fine mucous membrane which covers and joins the anterior surface of the eyeball to the posterior surface of eyelid. This translucent membrane lines the white part of the eye starting at the edge of the cornea (limbus) and runs behind the eye to cover the anterior part of the sclera. It then flows, loops forward, and forms the inside surface of the eyelids. At the medial canthus the conjunctiva fold thickens, which is called the semilunar fold. Figure 2. The different parts of the conjunctiva and its relation to other obit anatomy The conjunctiva is subdivided into three parts depending on location: palpebral conjunctiva, bulbar conjunctiva and conjunctival fornix. Histologically the conjunctiva is divided into three layers.From superficial to deep these are epithelial, adenoid and fibrous. These con‐ junctival layers contain a wide range of structures that includes glands, melanocytes, langer‐ hans cells, mast cells and lymphoid tissue. The arterial blood supply to conjunctiva is made up of branches of ophthalmic artery, the anterior and posterior conjunctival arteries. These are branches of anterior ciliary arteries and palpebral arcades respectively. The venous drainage follows the arteries. Posterior con‐ junctival veins drain the veins of the lid and anterior conjunctival veins drain anterior ciliary vein to ophthalmic vein. The lymphatic drainage of the conjunctiva depends on the region of the conjunctiva. Lym‐ phatics in palpebral region drain into the lymphatics of eyelids. In bulbar conjunctiva, lym‐ phatics from lateral side drain into the superficial preauricular lymph nodes & lymphatics from medial side drain to deep sub maxillary nodes. The first division of the trigeminal provides nerve supply to the conjunctiva. 1.2. Allergic and irritant conjunctivitis Before discussing the major contents of the chapter, it is necessary to briefly discuss allergic and irritant conjunctivitis. Infective Conjunctivitis – Its Pathogenesis, Management and Complications 23 http://dx.doi.org/10.5772/52462 Figure 3. Allergic conjunctivitis- look for follicles and papillae which are characteristic of allergic conjunctivitis Allergic conjunctivitis is seen in two acute disorders; seasonal allergic conjunctivitis (which is prevalent in the summer months) and perennial allergic conjunctivitis (which presents in‐ termittently) and three chronic disorders, vernal keratoconjunctivitis, atopic keratoconjunc‐ tivitis and giant papillary conjunctivitis. Allergic conjunctivitis is considered to be a type I hypersensitivity reaction. Its treatment is largely supportive, although in severe cases, topi‐ cal corticosteroids may be of some benefit 1. Figure 4. Irritant conjunctivitis- generalised redness around the eye and constant tearing are typical features Irritant conjunctivitis is a form of conjunctivitis that is often bought on by an external source. The source, considered an ‘irritant’, directly affects the conjunctiva, causing an in‐ flammatory response. Not all causes of irritant conjunctivitis are external however. Caus‐ es of irritant conjunctivitis are vast, though some of the more common causes are hair products (e.g. shampoos), smoke or fumes, chlorinated water used in swimming pools. A common non-external source is trapped eyelashes, which continually irritate the conjunc‐ tiva. Treatment of irritant conjunctivitis is thorough cleansing of the eye and removing the irritant. 24 Common Eye Infections 2. Infectious conjunctivitis Infective conjunctivitis can be caused by several bacterial and viral pathogens. Infective con‐ junctivitis can be further differentiated into acute infective conjunctivitis, defined as inflam‐ mation of the conjunctiva due to infection that does not last longer than 3 weeks, and chronic conjunctivitis, inflammation of the conjunctiva that lasts longer than 3 weeks. In the developed world, acute infectious conjunctivitis is a common presentation in the pri‐ mary care setting, accounting for up to 2% of consultations with the general practitioner [ 2]. Many general practitioners find it difficult to differentiate between bacterial and viral con‐ junctivitis. The uncertainty of the pathogenic cause of acute conjunctivitis has led to the rou‐ tine practice of prescribing a broad spectrum antibiotic topically even though the pathogen has not been proved to be bacterial in nature. In the UK, approximately 3.4 million topical antibiotic prescriptions are issued every year, at a cost to the NHS of over £4.7 million [3]. A diagnosis of conjunctivitis is usually made on the basis of a clinical history and examina‐ tion by the clinician. Other investigations of conjunctivitis, such as swabs and cultures of the conjunctiva are rarely performed as it often delays treatment and has very little prognostic benefit, as conjunctivitis is often a self limiting illness and the antibiotics currently used have a good spectrum of pathogen coverage. Swabs and cultures are mainly used in research pur‐ poses. It is vital that a correct diagnosis is made to early to identify the cause and start treatment promptly. It is also essential to rule out more serious causes and medical emergencies that would require hospital admission. Such cases would include bacterial keratitis, acute closed angle glaucoma, corneal abrasions and others. 2.1. Bacterial conjunctivitis Bacterial conjunctivitis is a relatively common infection and affects all people, although a higher incidence is seen in infants, school children and the elderly. Bacterial conjunctivitis has a higher prevalence in children, where a recent study by Rose et al identified 67% of 326 children as having a bacterial cause [4]. Although its incidence is continuing to decrease in developing nations, periodic rises in incidence are seen during the monsoon seasons in many countries such as Bangladesh, and thus, bacterial conjunctivitis is the most common cause of infective conjunctivitis in developing nations. 2.1.1. Types of bacterial conjunctivitis and pathogenic causes of bacterial conjunctivitis Bacterial conjunctivitis can be broadly split into three major categories; hyperacute bacterial conjunctivitis, acute conjuncitivis and chronic conjunctivitis. • Hyperacute bacterial conjunctivitis is commonly seen in patients affected with N. Gonor‐ rhoea. The onset is often rapid with an exaggerated form of conjunctival injection, chemosis and copious purulent discharge. Prompt treatment is essential to prevent complications. Infective Conjunctivitis – Its Pathogenesis, Management and Complications 25 http://dx.doi.org/10.5772/52462 • Acute bacterial conjunctivitis is the most commonly seen bacterial conjunctivitis and often presents with a typical presentation, time course and prognosis. In a study done by Weiss et al, the most common pathogens in acute bacterial conjunctivitis were Staphylococcus aureus, Haemophilus influenzae, streptococcus pneumoniae, and Moraxella catarrhalis, whereas in an older study done by Gigilotti et al, Chlamydia trachomatis was also commonly found in infected patients [5, 6]. • Chronic bacterial conjunctivitis, ie, red eye with purulent discharge persisting for longer than a few weeks, is generally caused by Chlamydia trachomatis or is associated with a nidus for infection such as in dacryocystitis [7]. In certain bacterial conjunctivitis, it is essential to identify a pathogen. As mentioned, most causes of conjunctivitis are diagnosed and treated on a clinical exam basis, but in patients who are particularly susceptible such as neonates or immunodeficient patients, a microbio‐ logical diagnosis must be made to exclude harmful pathogens such as N.gonorrheae, Listeria monocytogenes, Corynobacterium diptheriae and certain members of the Haemophilus group. These pathogens contain proteolytic enzymes which may cause long term damage to the pa‐ renchyma of the conjunctiva. 2.1.2. Signs and symptoms of bacterial conjunctivitis Although the symptoms of bacterial conjunctivitis are varied and quite vast, there are a number of key symptoms which differentiate it from other eye infections. Thick purulent discharge is seen as the major symptom that affects sufferers of bacterial conjunctivitis, com‐ pared to the watery discharge seen in viral conjunctivitis.